After doing a graft repair of a thoraco-abdominal aneurysm, the patients developed weakness. Most propable cause for this:

Aeria Radicularis Magna: Aeria radicularis magna (aery of Adamkiewicz) is the main source of blood supply to the anterior spinal aery in the thoracolumbar segment of the spinal cord. It arises from either one of the lower posterior intercostal aeries (T9-T11) or of the subcoastal aery (T12), or less frequently of the upper lumbar aeries (L1 and L2) Occlusion or interruption is one of the major reasons for spinal cord ischemia (leading to paraparesis/Paraplegia) during surgery for thoracoabdominal aneurysm. Ref: Sabiston 20th edition Pgno: 1788